1. Field of the Invention
The present invention relates to a control system for a hybrid vehicle, and in particular, to a control system for a cylinder deactivating type hybrid vehicle that can guarantee an appropriate amount of regeneration during deceleration.
2. Description of the Related Art
Conventionally, hybrid vehicles which carry motors as power sources for driving the vehicles in addition to the engine are known. There are two types of hybrid vehicles, and one of which is parallel hybrid vehicles in which the output of the engine is assisted by an electric motor.
This parallel hybrid vehicle assists the output of the engine by an electric motor during acceleration, and various controls such as carrying out the charging of the battery and the like by regenerative breaking during deceleration are executed, and while guaranteeing the remaining charge (electrical energy) of the battery, the demands of the driver can be satisfied. In addition, because structurally a mechanism that disposes the engine and electric motor in a straight row is formed, there are the merits that the structure can be simplified and the weight of the system as a whole can be made small, and the freedom of the mounting in the vehicle is high.
Here, in this parallel hybrid vehicle, a structure providing a clutch between the engine and electric motor in order to eliminate the influence of friction (engine brake) of the engine during regenerative braking (see for example, Japanese Unexamined Patent Application, First Publication, No. 2000-97068) and a structure in which the engine, electric motor, and transmission are joined in a series in order to implement an extreme simplification (see for example, Japanese Unexamined Patent Application, First Publication, No. 2000-125405) are known.
However, the former structure providing a clutch between the engine and electric motor as described above has the drawbacks of introducing complicates relating to the structure by providing a clutch and worsening mountability, and at the same time, the transfer efficiency of the transmission system deteriorates even during travel as a result of using a clutch. In contrast, a later structure in which the engine, electric motor, and transmission are joined in a series decreases the amount of regenerative braking by the amount of the friction equivalent to the engine described above, and thus there are the problems that the electrical energy that can be guaranteed by regeneration becomes small, and therefore, the amount of assistance that the electric motor provides is limited.
In addition, as a means of decreasing the friction of the engine during deceleration in the former type, there is the method of controlling the throttle valve at the opening side during deceleration using an electric control throttle mechanism and thus increasing the amount of regeneration by greatly decreasing the pumping loss. However, because new air flows as-is into the exhaust system in large amounts during deceleration, there is the problem that the temperatures of the catalyst and A/F sensor decrease, and this has harmful effects on the optimal control of the exhaust gas.
Thus, the present invention has the object of providing a control system for a hybrid vehicle that improves fuel consumption by the amount equivalent to the decrease in the engine friction decreases by making possible all cylinders deactivated operation, and at the same time, guarantees an optimal amount of regeneration during deceleration.